1. Field of the Invention
This invention relates to an imaging device using an electron tube which is capable of high-speed shuttering.
2. Related Background Art
As the prior art relevant to the imaging device according to this invention, the imaging devices as shown in FIGS. 1 and 2 are known. FIG. 1 is a sectional view of a photocathode gate-type imaging device. A vacuum vessel 201 includes a light detecting plate on which a photocathode 202 is formed, an output plate on which a fluorecent surface film 203 is formed, and a microchannel plate (MCP 204) located between the light detecting plate and the output plate for performing multiplication of electrons input thereto.
In this imaging device, when a gate voltage is applied to the photocathode 202, changed from 0 V to -200 V with bias voltages respectively applied +4.9 KV and +0.9 KV to the fluorescent surface film 203 and the MCP 204, a shuttering operation is conducted during a gate period in which the applied voltage is kept to be -200 V, and only during a gate period in which the applied voltage is kept to be -200 V, an image is obtained. That is, only during the gate period (T.sub.G), the photoelectrons emitted from the photocathode 202 reach the MCP 204, and an image corresponding to the gate period (T.sub.G) is formed.
FIG. 2 is a sectional view of an MCP gate-type imaging device. A vacuum vessel 201 includes an acceleration grid 205, an electron lens 206, a deflecting electrodes 207y, 207x, and grounded anodes 208, 209. In this imaging device, deflecting voltages are respectively applied to the deflecting electrodes 207x, 207y so that framing images are formed.
When a voltage is applied to the MCP 204 between both ends thereof, changed from 0 V to +800 V, photoelectrons are multiplied only during a gate period in which the applied voltage is kept to be +800 V. As in such photocathode gate-type imaging device, high-speed shuttering operation can be realized.